Smoke unit heating elements

Martin Derouin posted:

I got some 18 and 22ohm wire wound resistors from Digit Key, I am not overly impressed with the smoke out put, Is the blue coating suppose to be removed and if so, how much??

Marty

I have the same resistors. Yes, the ceramic coating should be removed so that the wires are exposed. It's fairly easy to do this with a Dremel rotary wire brush. Trouble is that you can break the wire winding if you apply too much force. The idea is just to take the ceramic coating off so that the wires are in direct contact with the smoke wadding.

Okay will give it a try, thanks

Marty

I should have asked which smoke unit you are intending to use these with (!) but assumed that it was an older TMCC smoke unit. These particular resistors are often used to replace the stock 27 ohm unit, which came wrapped in a fiber sleeve that pretty quickly gets charred. Even Lionel recommends removing the sleeve (as well as other steps described in a video you can see here: https://www.youtube.com/watch?v=ZkDlQ5Cwwlk).

Some manufacturers, in particular 3rd Rail, use ceramic coated resistors as heating elements and they work fine but I don't know the spec for these or indeed who made the smoke units they use.

If you are replacing a TMCC 27 ohm resistor I'd try the 22 ohm alternative first with the coating removed and see what difference that makes to the output. Legacy engines use a variety of wire wound resistors and these really have to be replaced with the identical parts because the voltage to them is regulated.

I have had better luck removing the ceramic coating by placing the resistor in a vise and slowly crushing it until it cracks, then pick away at the coating.

Pete

I routinely use the 20 ohm ones.  I take the powered ceramic off with the Dremel wire wheel.  The trick is to go slow rotation and gently work it until it starts to come off, then just follow it around.  Also, go in the direction of the winding and the wires rarely get damaged, I've only lost one in doing 30-40 of them.  I just hold it by one lead right at the resistor and gently run the wire wheel back and forth and peel off a section of the coating, then rotate slightly to allow the wheel to get a bite on a new section, etc.

I removed the coating as suggested and they work much better, I am putting them in post war American Flyer engines that I put can motors in, because they run at a much lower voltage...

Marty

You can also use some diode strings to reduce the voltage to the motors to allow more power to the smoke units.

John,

These post war AF smoke units come with a nichrome wire smoke unit usually with a resistance of 35 - 45 ohms. They are powered from the track power. If I want to use the heating resistor, with power from the rails [18v] in a locomotive converted to TMCC, should it be of a higher resistance than 20 ohms, say 35-45 ohms? If so I wonder if I would find one to fit in the American Flyer smoke unit.

Thanks                                                                                                                          Ray

TMCC locomotives feed the resistor half-wave track power except when you are boosting the smoke.  I've found that 20-22 ohms works well with TMCC locomotives for the smoke resistor.  This also keeps the smoke control triac well below maximum temperature ratings.